Method and device for improving voice quality on transparent telecommunication-transmission paths

ABSTRACT

The invention relates to a method and a device for improving voice quality on transparent telecommunications-transmission paths. The invention is characterised in that the audio-transmission channel is adapted to the respective audio-spectrum of the speaker at predetermined intervals. As a result, means for analysing the voice signals in relation to the useful band width and amplitude thereof are provided in addition to means for influencing the band width and amplitude of the audio-transmission channel according to the determined useful band and amplitude. Said means can be installed in the communication terminal as well as in the communication network.

[0001] The invention relates to a method and a device for improving voice quality on transparent telecommunications paths according to the preamble of the independent patent claims.

[0002] With transparent voice transmission channels, such as e.g. used in mobile telecommunication systems via GSM or UMTS standards, the digital voice signal is sent with no extra Radio Link Protocol (RLP). Radio Link Protocol a radio transmission route protocol that is transmitted in addition to the useable signal and also ensures quality of the data during transmission.

[0003] When using transparent transmission, the voice quality is influenced on the spokesperson's end by:

[0004] Interference occurring outside of the acoustic spectrum of the spokesperson but within the NF transmission band width of the telecommunication device, e.g. environmental noise.

[0005] Voice patterns of the spokesperson, e.g. inarticulate and/or speaking too quietly, as well as the language of the spokesperson.

[0006] Speaking too loudly only slightly affects the listeners ability to understand what is being said but can be uncomfortable.

[0007] There are already new known technical means of improving voice quality in telecommunications transmission.

[0008] According to DE 198 52 091 C1, an equalizer is routed into the audio path preferably between BSC and MSC. The equalizer compensates for the influences in audio quality between the two participating end devices.

[0009] The DE 198 52 805 A 1 processes signals from at least two microphones with a voice processing algorithm, whereby background interference noise is compensated by 180° phase angle rotation.

[0010] Both of these methods are associated with extra technical requirements in the end devices or in the communication network systems.

[0011] The task of the following invention is therefore to recommend a process and a system of suppressing environmental noise outside of the voice spectrum and to improve voice quality based on the audio spectrum and the individual volume of the spokesperson.

[0012] This task will be handled by means of the process based on claim 1 or the device based on claim 8 by adjusting the audio transmission channel in defined time intervals to the corresponding audio spectrum of the spokesperson. Solutions for this are included in a means of analyzing the voice signals according to the used band width and amplitude as well as a means of influencing the band width Δf and amplitude v of the audio transmission channel based on the used band width and amplitude that are determined. These means can be installed in the communication transmission devices and in the communication network itself.

[0013] The audio spectrum of voice signals is mainly determined through:

[0014] Voice: distinct differences result between vocal ranges, e.g. Roman languages with intonation on the formant and vocally soft, melodious languages with normally higher band widths and more dynamic in the volume such as Arabic for example.

[0015] Vocal register (tessitura), e.g. Soprano or tenor and tone color, i.e. the voice emission and spectrum of the formants.

[0016] Intonation which is mainly characterized as clear or unclear. Unclear intonation muffles formants.

[0017] Based on a preferred best-case instance of the invention, the voice signals are then analyzed in an analyzer for usable band width Δf, mid-range frequency f_(O) and amplitude v.

[0018] Control signals with voice signal information on the band width Δf, mid-range frequency f_(O) and amplitude v from the determined frequency/amplitude analysis parameters will then preferably be generated in a microprocessor.

[0019] Based on a preferred best-case instance of the invention, control signals are used on the determined mid-range frequency f_(O) and band width Δf of the voice signal for controlling a band pass filter whereas the transmission characteristics are defined in accordance with the determined parameters.

[0020] The control signal is also fed into a controllable amplifier along with the determined amplitude. The amplification is defined depending on the determined amplitude of the voice signal. To achieve optimal voice pattern recognition (optimally understandable), the amplifier has integrated logarithmic transmission characteristics.

[0021] Since the control signals are regenerated in timed intervals _(T) by the microprocessor, a quasi-continuous adjustment of the audio transmission channel to the voice spectrum of the spokesperson is achieved.

[0022] An example of an application in graphic representation FIG. 1 shows the invention in further detail. Further features, advantages and application possibilities can be attained from FIG. 1 and the corresponding description.

[0023] The device will preferably be installed in a telecommunications transmitting device between the microphone output or pre-amplifier and the following components (voice encoder in digital mobile telephones). Basically, it could also be installed in a communication network, e.g. in a network node.

[0024] The voice signal 7 (input signal) from the microphone is amplified by a first linear amplifier 1 to such a level that the signal can be analyzed according to the frequency and amplitude in an analyzer 2 in the next step. Broken down, the analyzer 2 will determine the signal band width Δf, mid-range frequency f_(O) and the amplitude v of the voice signal 7.

[0025] Three control signals 8-10 containing the information on the voice signal consisting of band width Δf, mid-range frequency f_(O) and amplitude v are generated from the determined parameters from the frequency/amplitude analysis in a control unit, e.g. a microprocessor 3.

[0026] These three control signals 8-10 are regenerated in time intervals _(T) (e.g. _(T)=5 sec.) by the microprocessor.

[0027] A clock generator 4 generating at _(T) causes a reset of the microprocessor 3 after which the control signal is determined again. The interval _(T) will preferably be able to be defined and can be set and optimized to the spokesperson.

[0028] The control signals 8, 9 are used with the determined mid-range frequency f_(O) and the band width of the voice signal for controlling a band pass filter 5 with transmission characteristics defined based on the determined parameters.

[0029] Just as an example, the useable transmission band width of the NF channel of a communication transmitting device is 300 to 3400 Hz.

[0030] The analyzer determines an actual band width for a given spokesperson of e.g. 350 to 2500 Hz at a mid-range frequency f_(O) of 1450 Hz however. The band pass filter 5 is adjusted to the determined values whereas interference signals which are outside of the defined cutoff frequencies of 350 Hz or 2550 Hz are effectively suppressed.

[0031] Using the device based on the invention, especially the adaptive band pass filter 5 which controls the mid-range and cutoff frequencies preferably via digital signals, the NF transmission characteristics are adjusted almost continuously in time intervals _(T) to the audio spectrum of the corresponding spokesperson, i.e. adapted to the voice, vocal register and intonation of the respectful spokesperson.

[0032] The voice signal is regulated for optimal understanding (generally boosted) using information 10 on the amplitude of the voice signal in a controlled amplifier 6 via preferably logarithmic response curves. The logarithmic response curve of this amplifier 6 puts the emphasis on the formats of a spokesperson whereby, especially for muffled intonation and vocally toned languages, the ability to understand the voice is greatly improved on the listening end.

[0033] Graphic Legend

[0034]1 Amplifier

[0035]2 Analyzer

[0036]3 Microprocessor

[0037]4 Clock generator

[0038]5 Band pass filter (controllable)

[0039]6 Amplifier (controllable)

[0040]7 Voice signal (input signal)

[0041]8 Control signal (mid-range frequency)

[0042]9 Control signal (band width)

[0043]10 Control signal (amplitude) 

1. Procedure for improving the quality of voice on transparent telecommunications transmission paths, indicated by, the audio transmission channel being in adjusted to the corresponding voice spectrum of the spokesperson in defined time intervals.
 2. Procedure according to claim 1, indicated by the voice signal being analyzed in an analyzer (2) for useable band width (Δf), mid-range frequency (f_(O)) and the amplitude (v).
 3. Procedure according to one of the previous claims indicated by control signals (8-10), containing information on the voice signals concerning band width (Δf), mid-range frequency (f_(O)) and the amplitude (v), being generated from the parameters determined from the frequency/amplitude analysis in a microprocessor (3).
 4. Procedure according to one of the previous claims indicated by the control signals (8, 9) using information from the determined mid-range frequency (f_(O)) and band width of the voice signal for controlling a band pass filter (5) for which the transmission characteristics are defined based on the determined parameters.
 5. Procedure according to one of the previous claims indicated by the control signal (10) being fed with the determined amplitude into a controllable amplifier (6) which amplifies in accordance with the determined amplitude of the voice signal.
 6. Procedure according to claim 5 indicated by the amplifier (6) containing logarithmic transmission characteristics.
 7. Procedure according to one of the previous claims indicated by the control signals (8-10) being regenerated by the microprocessor (3) in defined time intervals (_(T)).
 8. Device for utilizing the procedure based on one of the previous claims, indicated by, a means (2) of analyzing the voice signal (7) in reference to its used band width (Δf) and amplitude (v); a means (5; 6) of influencing the band width (Δf) and amplitude (v) of the audio transmission channel depending on the useable band width and amplitude.
 9. Device according to claim 8, indicated by, an analyzer (2) which analyzes the voice signal (7) for its band width (Δf), mid-range frequency (f_(O)) and the amplitude (v); a microprocessor (3) which generates control signals from the analyzed parameters; a band pass filter (5) which configures the voice signal based on the determined band width (Δf) and mid-range frequency (f_(O)); an amplifier (6) which amplifies based on the determined amplitude of the voice signal.
 10. Device according to one of claims 8 or 9 indicated by being able to be installed in a telecommunication transmission device between the output of the microphone or preamplifier and the following components.
 11. Device according to one of claims 8 or 9 indicated by being able to be installed in a telecommunications network. 